Amorphous iron oxide nanoparticles were synthesized by pulsed-laser deposition (PLD) for functionalization of indium-tin oxide surfaces, resulting in electrodes capable of efficient catalysis in water oxidation. These electrodes, based on earth-abundant and nonhazardous iron metal, are able to sustain high current densities (up to 20 mA/cm2) at reasonably low applied potential (1.64 V at pH 11.8 vs reversible hydrogen electrode) for more than 1 h when employed as anodes for electrochemical water oxidation. The good catalytic performance proves the validity of PLD as a method to prepare nanostructured solid-state materials for catalysis, enabling control over critical properties such as surface coverage and morphology.

Integrated absorber/electrocatalyst schemes are increasingly adopted in the design of photoelectrodes for photoelectrochemical cells because they can take advantage of separately optimized components. Such schemes also lead to the emergence of novel challenges, among which parasitic light absorption and the nature of the absorber/catalyst junction features prominently. By taking advantage of the versatility of pulsed-laser deposition technique, we fabricated a porous iron(III) oxide nanoparticle-assembled coating that is both transparent to visible light and active as an electrocatalyst for water oxidation. Compared to a compact morphology, the porous catalyst used to functionalize crystalline hematite photoanodes exhibits a superior photoresponse, resulting in a drastic lowering of the photocurrent overpotential (about 200 mV) and a concomitant 5-fold increase in photocurrents at 1.23 V versus reversible hydrogen electrode. Photoelectrochemical impedance spectroscopy indicated a large increase in trapped surface hole capacitance coupled with a decreased charge transfer resistance, consistent with the possible formation of an adaptive junction between the absorber and the porous nanostructured catalyst. The observed effect is among the most prominent reported for the coupling of an electrocatalyst with a thin layer absorber.

We report an X-ray absorption near edge structure (XANES) study of vanadium (V) and nitrogen (N) dopants in anatase TiO thin films deposited by radio-frequency magnetron sputtering. Measurements at the Ti K and V K edges were combined with soft X-ray experiments at the Ti L, O K and N K edges. Full potential ab initio spectral simulations of the V, O and N K-edges were carried out for different possible configurations of substitutional and interstitial dopant-related point defects in the anatase structure. The comparison between experiments and simulations demonstrates that V occupies substitutional cationic sites (replacing Ti) irrespective of the film structure and dopant concentration (up to 4.5 at%). On the other hand, N is found both in substitutional anionic sites (replacing O) and as N dimers within TiO interstices. The dopants' local structures are discussed with reference to the enhanced optical absorption and photocatalytic activity achieved by (co)doping.

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Cu−N codoped TiO 2 anatase thin films with a nanocolumnar architecture have been synthesized by RF-magnetron sputtering and characterized by Raman, scanning electron spectroscopy, and X-photoelectron spectroscopy. Absorption, photoluminescence, and photoluminescence lifetimes of the prepared samples have been investigated to understand the dynamics of the photogenerated carriers in connection to both introduced defects and the modified TiO 2 band structure. At low concentrations Cu is mainly present as Cu + , while at higher concentrations the Cu 2+ oxidation state prevails. Nitrogen, at low concentration and without the presence of copper dopant, substitutionally replaces oxygen to form a O−Ti−N linkage. With increasing concentration, interstitial nitrogen and Ti−O−N and Ti−O−N−O linkages are observed. In all codoped samples nitrogen is present as both interstitial and substitutional dopant. From photoluminescence spectra it is observed that nitrogen, in cooperation with Cu, more heavily affects the oxide structure, through Ti−N linkages, in such a way to quench the TiO 2 exciton luminescence through charge trapping or energy transfer mechanisms. Time-resolved PL analysis evidenced that Cu−N codoping hinders the exciton radiative recombination in the anatase network, giving rise to increase of both the mean lifetime and trapping rate on defects at the nanocolumn surface.

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